Lubricating oil compositions



United States Patent 3,282,842 LUBRICATING OIL COMPOSITIONS Francis J. lionner, Wilmington, DeL, and Nicholas V.

Messina, Glassboro, Ni, assignors to Mobil Oil Corporation, a corporation of New York No Drawing. Filed Mar. 6, 1964, Ser. No. 350,098 14 Claims. (Cl. 25251.5)

OH R l 0 Jl R RI! wherein R, R and R" each represents a member of the group consisting of hydrogen, halogen, alkyl, alkoxy and hydroxy;

(II) Compounds represented by the general formula OH R Q R R RI! wherein R, R and R" have the same meanin s as given above with reference to the first-given formula; and (III) Compounds represented by the general formula wherein R represents a member of the group consisting of hydrogen and alkyl; and R"" has the same meaning as R, R and R".

In the above formulas R, R and R in Formulas I and II, and R" in Formula III can be any halogen, i.e., chlorine, bromine, fluorine or iodine. Illustrative examples of alkyl radicals that the various Rs in the aboveidentified formulas may be are alkyl (including cycloalkyl) radicals containing, for example, from 1 to about 18 carbon atoms. The alkyl radical can be either straightor branched-chained. Illustrative examples of alkoxy radicals (i.e., radicals that may be represented by the formula --OR) that R, R, R and R" where they appear in the foregoing formulas may be are alkoxy radicals wherein the alkyl grouping thereof is of the same scope as given above with reference to the alkyl groupings that R, R, R" and R"" in the aforesaid formulas may be.

Lubricating oils, especially turbine oils, and, more particularly, marine turbine oils, are subjected to severe oxidation and rusting conditions. In such lubricating applications the oil used as a lubricant for turbine bearings absorbs considerable. heat and reaches a quite high temperature. The high temperatures and the presence of air promote oxidation of the oil with consequent formation of acidic products and products that are insoluble in the oil, particularly when the oil contacts the cold cooling coils and other parts of the system where the temperature is relatively low. These insoluble materials may settle out and be deposited on governor parts, in bearing passages, in coolers, strainers and oil reservoirs ice where their accumulation can interfere with the supply of oil to bearings and with governor operation. Likewise, severe rusting conditions are encountered due to contamination of the oil with water from leaking shafts, condensation of humid air in the oil reservoir and bearing pedestals, water leaks in oil coolers, etc.

In view of the foregoing conditions, it has become the practice in the art to fortify various lubricating oils, especially marine turbine oils, by adding thereto chemical additives that enable such oils to resist oxidation and provide maximum protection against rusting.

One class of commonly used antioxidants are diaryl amines, such as diaryl amines, di-alkaryl amines and arylalkaryl amines, with the aryl groups preferably having not more than five benzene rings and the alkyl substituents, when present, preferably having not more than about 24 carbon atoms. Specific examples of such amines include phenyl-alpha-naphthylamine, phenyl-beta-naphthylamines, biphenyl-alpha-naphthylamine, tolyl-alphanap-hthylamine, tolyl-beta-naphthylamine, p,p'-diotcyldiphenylamine and p,p'-didecyl-diphenylamine.

Other commonly used antioxidants include various phenols or phenolic-type compounds, particularly alkylated phenols, e.g., 2,6-di-t-buty1-2-methylphen01, 2,4,6- tri-t-butylphenol, etc., phosphorus derivatives, e.g., zinc di-phenyldithiophosphate, etc.; as well as others. Corrosion inhibitors or anti-rust agents also are commonly employed in turbine oils. One class of such agents comprises compounds produced by first reacting a monocarboxylic acid with a poly-alkylenepolyamine and then reacting the resulting product with an alkenyl succinic acid anhydride. This class of anti-rust agents and their method of preparation are fully described in US. Patent No. 2,568,876, dated September 25, 1951. As shown in that patent, the monocarboxylic acid is reacted with the poly-alkylenepolyam-ine in a mole ratio varying between about 1 to 1 and about x-l to 1, respectively, where x represents the number of nitrogen atonis in the polyalkylene-polyamine molecule. The alkenyl succinic acid anhydride is then reacted with the intermediate product in a molar ratio varying between about x1 to 1 and about 1 to 1, respectively, the sum of the number of moles of the monocarboxylic acid and of the alkenyl succinic acid anhydride reacted with each mole of the polyalkylenepolyamine being no greater than x. A specific product of this type which is used in illustrating the instant invention is one prepared from oleic acid, tri-ethylenetetramine and tet'rapropenyl succinic acid anhydride (the preparation of which is illustrated in Example 1 of US. Patent No. 2,991,250, dated July 4, 1961), and which may be described more specifically as being a reaction product formed by reacting about 1 /3 molar proportions of oleic acid with 1 molar proportion of triethylenetetramine to form an intermediate product and then reacting about 1 molar proportion of the intermediate product with 2 molar proportions of tetrapropenyl succinic anhydride.

Darkening of lubricating oils in use, particularly turbine oils, is indicative of the extent of oxidative deterioration of the oil. Such darkening occurs to a marked degree with oils containing an amine antioxidant. This has been especially true in the case of those lubricating oil compositions wherein the base lubricating oil was derived from a crude oil of domestic origin, e.g., East Texas, or a crude oil having approximately the same or equivalent characteristics.

The present invention is based on our discovery that compounds of the kind embraced by Formulas I, II and HI, hereinabove, especially when used in conjunction with an amine antioxidant, render the oil resistant to discoloration, that is, they inhibit discoloration of the oil. In a further embodiment of the invention, it has been found that the discoloration inhibitors also provide a synergistic antioxidant improving effect when used in a turbine oil in combination with conventional amine-type and phenolic-type antioxidants.

Illustrative examples of compounds embraced by Formula I and which can be used in practicing the present invention are:

2,4-dihydroxybenzophenone 2,2-dihydroxybenzophenone 2-hydroxy-4-methoxy-4'-bromobenzophenone 2-hydroxy-4-rnethoxy-4-chlorobenzophenone 2-hydroxy-4-methoxy-4-butylbenzophenone 2-hydroxy-4-methoxy-4-methylbenzophenone 2hydroxy-4-methoxy-4'-ethylbenzophenone 2-hydroxy-4-ethoxy-4-methylbenzophenone 2-ethoxy-4-ethoxy-4-propylbenzophenone 2-hydroxy-4,4-diethoxybenzophenone 2-hydroxy-4-ethoxy-4-butoxybenzophenone 2-hydroxy-4-ethoxy-4-bromobenzophenone 2-hydroxy-4-ethoxy-4-chlorobenzophenone 2-hydroxy-4-ethoxy-4'butylbenzophenone 2-hydr-oxy-4-ethoxy-4-methoxybenzophenone 2-hydroxy-4-ethoxy-4-propoxybenzophenone 2-hydroxy-4,4,5 -trimethoxybenzophenone 2-hydroxy-4-butoxy-4',5 '-dimethoxybenzophenone 2-hydroxy-4-propoxy-4',6'-dichlorobenzophenone 2-hydroxy-4-butoxybenzophenone 2-hydroxy-4-methoxybenzophenone 2-hydroxy-4-ethoxybenzophenone 2-hydroxy-4-propoxybenzophenone 2-hydroxy-4-methoxy-4-propylbenzophenone 2-hydroxy-4-methoxy-4-tert.-butylbenzophenone 2-hydroxy-4-methoxy-4-iodobenzophenone 2-hydroxy-4-methoxy-2'-chlorobenzophenone 2-hydroxy-4-ethoxy-4'-ethylbenzophen-one 2-hydroxy-4,4-dimethoxybenzophenone 2-hydroxy-4,4'-dimethoxy-Z'-ethylbenzophenone 2-hydroxy-4,4',5 '-trimethoxybenzophenone 2-hydroxy-4,4-dimethoxy-3 -rnethylbenzophenone 2-hydroxy-4-propoxy-4',6-dibromobenzophenone 2-hydroxy-4,4,6-tributoxybenzophenone 2-hydroxy-4-ethoxy-2',4'-dibutylbenzophenone 2,3 '-dihydroxy-4-methoxy-4-butoxybenzophenone 2,2-dihydroxy-4,4-dimethoxybenzophenone 2,2-dihydroxy-4,4'-dipropoxybenzophenone 2,2-dihydroxy-4-methoxy-4-ethoxybenzophenone 2-hydroxy-4-methoxy-4'-fluorobenzophenone 2,2'-dihydroxy-4-methoxy-4-butoxybenzophenone 2,2'-dihydroxy-4-ethoxy-4'-butoxybenzophenone 2,2'-dihydroxy-4,4'-diethoxybenzophenone 2,2-dihydroxy-4-methoxy-4-propoxybenzophenone 2,2-dihydroxy-4,4'-dibutoxybenzophenone 2,3 dihydroxy-4,4-dimethoxybenzophenone 2,2',4,4-tetrahydroxybenzophenone From the foregoing illustrative examples of representative compounds of the kind embraced by Formula I, it will be noted that the 3, 4, 5, 6, 2', 3', 4', 5 and 6' positions may be unsubstituted or there may be, for example, either one or two substituents from the categories hereinbefore mentioned by way of example. These include, for example, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, butoxy, or hydroxy radicals, or a chlorine, bromine, fluorine or iodine atom. Other examples will be apparent to those skilled in the art from the foregoing illustrative examples and from the. examples represented by R, R and R" in Formula I.

Illustrative examples of compounds embraced by Formula II and which can be employed in practicing the instant invention are:

4-alkylphenyl-2'-hydroxybenzoates, e.g., 4-tert.-butylphenyl 2-hyclroxybenzoate (4-tert.-butylphenyl salicylate) Z-hydroxyphenyl-Z'-hydroxybenzoate 2,4-dihydroxyphenyl-2,4-dihydroxybenzoate 2,4-dihydroxyphenyl-2'-hydroxy-4',5-dialkoxy (e.g., di-

methoxy-, dibutoxy, etc.) benzoates 2-hydroxyphenyl-2-hydroxy-4'-butoxybenzoate 2,4-dipropylphenyl2'-hydroxy-4-chlorobenzoate 2-br0mophenyl-2-hydroxy-4-nonylbenzoate 2,4-dialkoxy-(e.g., dimethoxy-, diethoxy-, etc.) phenyl-2'- dihydroxy-4'-amylbenzoate Illustrative examples of compounds embraced by Formula II and which can be used in practicing the present invention are:

N-(2-hydroxyphenyl) benzotriazole N-(2-hydroxy-4-alkylphenyl) benzotriazole, e.g., N-(2- hydroxy-4-tert.-butylphenyl) benzotriazole N-(2-hydroxy-3-alkylphenyl) 3-alkylbenzotriazole, e.g.,

N- 2-hydroxy-3 -methylphenyl) 3 '-amylbenzotriazole N-(2-hydroxy-5-alkylphenyl) benzotriazole, e.g., N-(2- hydroxy-3-amylphenyl) benzotriazole N-(Z-hydroxyphenyl) 5'-propylbenzotriazole N- 2-hydroxy-5-chlorophenyl) 5 -octylbenzotriazole N- 2-hydroxy-4-rnethoxyphenyl) 3 -butylbenzotriazole N-(2,4-dihydroxyphenyl) 4-methylbenzotriazole N-(2-hydroxy-4-bromophenyl) 5' ethylbenzotriazole N-(2-hydroxy-5-butoxyphenyl) 4'-propylbenzotriazo1e N-(2-hydroxy-3-hexoxyphenyl) 3'-decylbenzotriazole Other examples of compounds embraced by Formulas II and III will be readily apparent to those skilled in the art from the foregoing examples of benzoates embraced by Formula II and of benzotriazoles embraced by Formula III, especially when considered in the light of the specific examples of benzophenones embraced by Formula I and from the examples of substituents represented by R, R and R" in Formula II.

The amount of discoloration inhibitor may be considerably varied but usually constitutes from about 0.005% to about 5%, preferably from about 0.01% to about 3%, by weight of the lubricating oil in which it is incorporated, the maximum amount within these ranges being influenced by the oil solubility of the particular discoloration inhibitor.

When the discoloration inhibitor is employed in the relationship whereby optimum value is obtained therefrom, that is, in conjunction with an amine antioxidant and/or one or more other antioxidants commonly employed in turbine and other lubricating oils, this additive (i.e., discoloration inhibitor) generally constitutes from about 0.05% to about 3% preferably from about 0.1% to about 2%, by weight, of the lubricating oil composition while the antioxidant will generally be present in amounts of from about 0.1% to about 5%.

When an anti-rust agent also is a component of the lubricating oil composition, it is usually employed in an amount corresponding to about 0.01% to about 1%, by weight, of the lubricating oil.

If an extreme pressure agent, e.g., tris-(2-chloropropyl) thionophosphate, is an additional modifier of the oil, it may constitute from about 0.25% to about 5%, usually between about 1% and about 3%, by weight, of the oil.

A full understanding of the present invention can be had by reference to the following examples which are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise Stated EXAMPLE 1 This example illustrates the suppression of darkening of a typical turbine oil containing an amine anti-oxidant, by incorporating therein a discoloration inhibitor of the invention. i

The turbine oil used was a low-sulfur content solventrefined East Texas crude having an SUV viscosity of 150 at F., containing 0.25% phenyl alpha naphthylamine and 0.04% of a rust inhibitor produced as briefly described hereinbefore and more fully in US. Patent No. 2,991,250. It consists of about equal parts of process oil and a reaction product of tetrapropenyl succinic anhydride and oleic acidtriethylene tetramine intermediate.

The color inhibitors used were (1) Univul D49, described by the vendor, General Aniline and Film Corporation, New York, N.Y., as 2,2-dihydroxy-4,4-dimethoxybenzophenone and (2) Tinuvin P, described by the vendor, Geigy Chemical Corporation, as 2(2-hydroxy- 5 -methylphenyl) benzotriazole.

The turbine oil per se and portions thereof having the color-formation inhibitors of the invention added thereto were subjected to the standard A.S.T.M. oxidation test D94354 titled: Oxidation Characteristics of Inhibited Steam-Turbine Oils. In this oxidation test 300 cc. of oil is held at 95 C. in the presence of water, oxygen and iron and copper metals. The color of the oil during this oxidation test was periodically measured by the Socony Mobil Color-Test Method. Briefly, this test is as follows. The lubricating oil sample is filtered and placed in the cell of a Beckman Model B spectrophotometer and the percent transmittance at wave lengths of 430, 520, 610 and 700 millimicrons is measured. The color of the oil is expressed as a single number calculated from the light transmittance at the four wave lengths.

Referring to Table I, the color values indicate the color of the lubricating oil at the end of various periods of time during the oxidation test, the higher the value the darker the oil. The darkening of the oil as the test proceeds gives indication of the extent of oxidative deterioration of the oil. It is seen that Tinuvin P significantly decreased the rate of darkening of the oil containing 0.04% of a rust inhibitor and 0.25% of a typical amine antioxidant. Also, Univul D49 decreased both the rate of darkening of the same base oil and the extent to which the oil had darkened at the end of the test.

As pointed out hereinabove, the discoloration inhibitors of the invention also have been found to provide a synergistic antioxidant improving effect in combination with conventional amine and phenolic type antioxidants as illustrated by Examples 2, 3 and 4. The test used was the well-known Catalytic Oxidation Test (C.O.T.).

Catalytic oxidation test This test determines the elfectiveness of an additive in preventing catalytic oxidation of an oil under oxidizing conditions. The test procedure is as follows. In a 200 x 25 mm. test tube is placed a 25 cc. sample of test oil having immersed therein (a) 15.6 sq. in. of sand-blasted iron wire, (b) 0.78 sq. in. of polished copper wire, (c) 0.87 sq. in. of polished aluminum wire and (d) 0.167 sq. in. of a polished lead specimen. The oil is heated to a temperature of 325 F. and maintained at this temperature, while dry air is being passed therethrough at a rate of liters per hour for 40 hours. The test results are reported in terms of the increase in Neutralization Number (N.N.) and increase in viscosity at 210 F. for the test oil as measured at the completion of the test. The greater the increase N.N. and viscosity the greater the oxidation which has taken place in the oil.

The base oil used in the tests was a typical base turbine oil, i.e., a solvent-refined East Texas oil of about 150 SUV at 100 F.

6 EXAMPLE 2 The antioxidant used in this example was phenyl alpha naphthylamine (PAN) and the inhibitor in accordance with the invention was 4-tert.-butylphenylsalicylate (TBS). The test results are shown in Table 1.1.

TABLE II Percent Cs. Increase Example Composition Vis. at in N eut. 210 F. Number Increase The data in Table II show the synergistic effect obtained by using a combination of PAN and TBS whereby better oxidation stability of the turbine oil is secured than when either additive is employed alone.

EXAMPLE 3 This example is similar to Example 2 except that the comparison involves the use of a difierent antioxidant in the oil composition, viz., a phenolic antioxidant, specifically di-tert.-butyl-p-cresol. The test results are given 1 Di-tert butyl-p-cresol.

The results in Table III show that the discoloration inhibitor TBS is more effective as an oxidation stabilizer for the oil is the phenolic antioxidant Paranox 441. The results further show the synergistic effect (although less pronounced than when using PAN) that is obtained by employing a combination of TBS and Paranox 441 (see 3-D) as additives to a turbine oil to improve its oxidation stability.

EXAMPLE 4 In this example the phenyl alpha naphthylamine antioxidant was used with a different discoloration inhibitor, viz., HCB, i.e., Dow light absorber HCB which is a 2 hydroxy-S-chloro benzophenone. The compositions and test results are given in Table IV.

TABLE IV Percent Cs. Increase Example Composition Vis. at in Neut. 210 F. Number Increase The results show that the same synergistic effect noted with a combination of PAN antioxidant and discoloration inhibitor TBS as additives to a turbine oil to increase its oxidation stability is also obtained when using a combination of PAN and a different discoloration inhibitor, namely HCB, as additives to the same turbine oil.

It will be understood, of course, by those skilled in the art that the present invention is not limited to the specific oil compositions containing the specific additives in the specific proportions set forth in the foregoing examples by way of illustration. Thus,-instead of the particular discoloration inhibitors employed in the individual examples one can use any other compounds embraced by Formulas I, H and III or a plurality of such compounds. For instance, instead of using 2,2-dihydroxy-4,4'-dimethoxybenzophenone alone as in Example 1, one can use a mixture of said compound and 2,2',4,4-tetrahydroxybeuzophenone.

Those skilled in the art also will understand that amine and phenolic antioxidants and rust inhibitors different from those specifically employed in the individual examples or mentioned herein may be employed in the compositions of this invention.

We claim:

1. A lubricating oil composition comprising a major amount of a mineral lubricating oil which normally discolors during use and a minor amount sufiicient to inhibit discoloration and oxidation of said oil of an oil-soluble inhibitor, said inhibitor comprising at least one member of the group consisting of:

(I) Compounds represented by the general formula wherein R, R and R" each represents a member of the group consisting of hydrogen, halogen, alkyl, alkoxy and hydroxy;

(II) Compounds represented by the general formula wherein R, R and R" have the same meansings as given above with reference to the first-given formula; and

(III) Compounds respresented by the general formula 2. A lubricating oil according to claim 1 wherein the inhibitor is 2(2-hydroxy-5-methylphenyl) benzotriazole.

3. A lubricating oil according to claim 1 wherein the inhibitor is 2,2-dihydroxy-4,4'-dimethoxybenzophenone.

4. A lubricating oil according to claim 1 wherein the inhibitor is 4-tertiary butylphenysalicylate.

5. A lubricating oil according to claim 1 wherein the inhibitor is 2-hydroxy-5-chloro-benzophenone.

6. A lubricating oil according to claim 1 which contains a minor amount suflicient to inhibit oxidation of an aromatic amine antioxidant.

7. A lubricating oil according to claim 1 which contains a minor amount sufiicient to inhibit oxidation of a phenolic antioxidant.

8. A lubricating oil according to claim 1 which contains a minor amount suificient to inhibit oxidation of phenyl alpha-naphthylamine.

9. A lubricating oil according to claim 1 which contains a minor amount sufficient to inhibit discoloration of said oil of compound II and a minor amount sufficient to inhibit oxidation of d-i-tertiary butyl para-cresol.

10. A lubricating oil according to claim 1 in which the inhibitor is 2,2-dihydroxy-4,4'-dimethoxybenzo phenone, and which also contains a minor amount sufficient to inhibit oxidation of phenyl al-pha-naphthylamine.

11. A lubricating oil according to claim 1 in which the inhibitor is 2(2'-hydroxy-5-methylphenyl) benzotriazole and which also contains a minor amount sufficient to inhibit oxidation of. phenyl alpha-naphthylamine.

12. A lubricating oil according to claim 1 in which the inhibitor is 4-tertiary butyl phenylsalicylate and which also contains a minor amount sufficient to inhibit oxidation of phenyl alpha-naphthylamine.

13. A lubricating oil according to claim 1 in which the inhibitor is 4-te1tiary butyl phenylsalicylate and which also contains a minor amount suflicient to inhibit oxidation of di-tertiary butyl para-cresol.

14. A lubricating oil according to claim 1 in which the inhibitor is Z-hydroxy-S-chloro-benzophenone and which also contains a minor amount sufficient to inhibit oxidation of phenyl alpha-naphthylamine.

References Cited by the Examiner UNITED STATES PATENTS 2,202,877 6/ 1940 Stevens et a1 25252 X 2,410,652 11/1946 Griffin et al 25250 X 2,861,952 11/1958 Thompson et a1 25250 2,876,210 3/1959 Wynn et :al. 252404 X 3,018,269 1/1962 Bruno 252403 X 3,094,488 6/ 1963 Beerbower et al 25251.5 3,112,338 11/1963 Smutny et al 252-404 X DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL WHICH NORMALLY DISCOLORS DURING USE AND A MINOR AMOUNT SUFFICIENT TO INHIBIT DISCOLORATION AND OXIDATION OF SAID OIL OF AN OIL-SOLUBLE INHIBITOR, SAID INHIBITOR COMPRISING AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF: (I) COMPOUNDS REPRESENTED BY THE GENERAL FORMULA 